In on-court sports such as tennis, volleyball, and basketball, involving rapid movements forward, backward, left and right, a sport shoe needs to hold the front foot portion by an upper skin in order to prevent injuries in the foot portion. Therefore, the material of an upper skin is required to be non-stretchable and have a high strength. An upper skin is often reinforced with artificial leather, synthetic leather or a belt.
Such an upper skin has a high rigidity. Therefore, the upper skin less easily fits to the foot. For example, when raising the heel portion as is done frequently in such on-court sports as described above, when raising the heel and twisting the heel inwardly, and when raising the heel and twisting the heel outwardly, the front foot portion of the upper will have a large ruck, whereby the toe is easily compressed locally.